# CertCache.java

    /*
     *  Licensed to the Apache Software Foundation (ASF) under one
     *  or more contributor license agreements.  See the NOTICE file
     *  distributed with this work for additional information
     *  regarding copyright ownership.  The ASF licenses this file
     *  to you under the Apache License, Version 2.0 (the
     *  "License"); you may not use this file except in compliance
     *  with the License.  You may obtain a copy of the License at
     *
     *   http://www.apache.org/licenses/LICENSE-2.0
     *
     *  Unless required by applicable law or agreed to in writing,
     *  software distributed under the License is distributed on an
     *   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
     *  KIND, either express or implied.  See the License for the
     *  specific language governing permissions and limitations
     *  under the License.
     */
    package org.apache.synapse.transport.certificatevalidation.cache;

    import org.apache.commons.logging.Log;
    import org.apache.commons.logging.LogFactory;
    import org.apache.synapse.transport.certificatevalidation.Constants;

    import java.security.cert.X509Certificate;
    import java.util.Iterator;
    import java.util.Map;
    import java.util.concurrent.ConcurrentHashMap;

    /**
     * This is a cache to store a certificate against a unique string (can be a serial number). This is a singleton since
     * more than one cache of this kind should not be allowed. This cache can be used by any place where certificate
     * caching is needed.
     */
    public class CertCache implements ManageableCache {

        private static volatile CertCache cache;
        private static volatile Map<String, CertCacheValue> hashMap = new ConcurrentHashMap<String, CertCacheValue>();
        private static volatile Iterator<Map.Entry<String, CertCacheValue>> iterator = hashMap.entrySet().iterator();
        private static volatile CacheManager cacheManager;
        private static final Log log = LogFactory.getLog(CertCache.class);

        private CertCache() {
        }

        public static CertCache getCache() {
            //Double-checked locking
            if (cache == null) {
                synchronized (CertCache.class) {
                    if (cache == null) {
                        cache = new CertCache();
                        cacheManager = new CacheManager(cache, Constants.CACHE_DEFAULT_ALLOCATED_SIZE,
                                Constants.CACHE_DEFAULT_DELAY_MINS);
                    }
                }
            }
            return cache;
        }

        public synchronized X509Certificate getCacheValue(String serialNumber) {
            CertCacheValue cacheValue = hashMap.get(serialNumber);
            if (cacheValue != null) {
                return cacheValue.getValue();
            } else
                return null;
        }

        @Override
        public ManageableCacheValue getNextCacheValue() {

            if (iterator.hasNext()) {
                return hashMap.get(iterator.next().getKey());
            } else {
                resetIterator();
                return null;
            }
        }

        @Override
        public int getCacheSize() {

            return hashMap.size();
        }

        @Override
        public void resetIterator() {

            iterator = hashMap.entrySet().iterator();
        }

        public static void resetCache() {

            hashMap.clear();
        }

        public synchronized void setCacheValue(String serialNumber, X509Certificate cert) {
            CertCacheValue cacheValue = new CertCacheValue(serialNumber, cert);

            if (log.isDebugEnabled()) {
                log.debug("Before set - HashMap size " + hashMap.size());
            }
            hashMap.put(serialNumber, cacheValue);
            if (log.isDebugEnabled()) {
                log.debug("After set - HashMap size " + hashMap.size());
            }
        }

        public synchronized void removeCacheValue(String serialNumber) {

            if (log.isDebugEnabled()) {
                log.debug("Before remove - HashMap size " + hashMap.size());
            }
            hashMap.remove(serialNumber);
            if (log.isDebugEnabled()) {
                log.debug("After remove - HashMap size " + hashMap.size());
            }
        }

        /**
         * This is the wrapper class of the actual cache value.
         */
        private class CertCacheValue implements ManageableCacheValue {

            private final String serialNumber;
            private final X509Certificate issuerCertificate;
            private final long timeStamp = System.currentTimeMillis();

            public CertCacheValue(String serialNumber, X509Certificate issuerCertificate) {

                this.serialNumber = serialNumber;
                this.issuerCertificate = issuerCertificate;
            }

            public X509Certificate getValue() {

                return issuerCertificate;
            }

            public String getKey() {

                return serialNumber;
            }

            public boolean isValid() {

                // Will be always return true since we only set defined data.
                return true;
            }

            public long getTimeStamp() {

                return timeStamp;
            }

            /**
             * Used by cacheManager to remove invalid entries.
             */
            public void removeThisCacheValue() {

                removeCacheValue(serialNumber);
            }

            public void updateCacheWithNewValue() {
                // No implementation needed since there are no scenarios of the cache value being invalid.
            }
        }
    }